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by doukdouk 2129 days ago
I don't think such calculations are particularly useful, maybe about as much as Paul Graham's wealth tax "model". The reason is that tax codes are way more complicated than just nominal tax rates.

Did you know, for instance, that you taxable income is 90% of your real income [0]? So the 45% rate kicks in at a 175,340€ wage, not actually 157,806€.

Anyway, it does not matter because of the unusually large income splitting [1]. If both adults have a 157,806€ wage and say, two kids, the total income would be 315,612 with three fiscal shares, and thus would pay 3 times the amount of taxes owed for a 315,612/3 income (i.e. 105204€), where the marginal tax rate is 30%, not 45% [2].

Anyway, it does not matter either because the main income tax in France is not the "income tax", but the "generalized social contribution" (flat rate).

My point is not to write an essay on French taxation, but to show that simply comparing tax brackets and rates is useless, since the definition of "taxable income" is not the same between different countries, how brackets, rates and taxable income are used to actually compute the tax amount is not straightforward, there are many others taxes, and so forth.

[0] https://www.impots.gouv.fr/portail/particulier/questions/com...

[1] https://en.wikipedia.org/wiki/Income_splitting

[2] Amount of tax is number of n T(i/n), where i is income, T is the function which maps income to taxes owed and n is the number of fiscal shares. Because T is convex, n T(i/n) is less than T(i).